if youre new - new to welding forget making anything at first and just concentrate on getting good consistent - penetrating welds.

start with the simplest conditions and work your way up.

get some hunks of clean material (mild .120 or so) and go at it till you can pull off decent laps, butts, fillets, etc. while your at a bench. then start playing with thickness, go thin wall and youll be shocked how different it is. then positions, anyone whos wheeled much has enjoyed being showered in molten bbs while fixing something welding upside down. got all that covered ? move into stainless and aluminum, high carb stuff, castings - all very different acting materials even though the principle is the same. theres more but thats a start -

then again ,theres always books on the topic -
but youll catch on qiucker if you just start doing it and then go back and figure out why something works the way it does.

when we got our welder i just took some plate and welded different things to it like nuts, bolts, washers, other plate. Weld them different ways trying new things like circle motion, C pattern, stuff like that. Try different wire speeds and heat ranges

One thing no-one has mentioned here, but after you make some welds, section them with a saw, and look to see the penetration. You might want to get some dye, or alcohol with dye in it, and put it on the weld, it will highlight cracks that you can't see with the naked eye.

Thats the real key, getting a solid weld that goes all the way through where you want it to.

Doing something like getting some 1/4" thick steel, and make the same welds with different speeds, and different heat settings. That will help you learn which settings to us for which thickness of metal.

Of course, don't overlook a decent welding textbook. They do provide some decent info.